A cellulose production method

ABSTRACT

The invention relates to the chemical industry, namely to the production method of cellulose from all types of plant cellulose-containing raw material. The method includes raw material impregnation and hydrolysis in a hydrolysis solution, cellulose filtration, washing with water, filtration and drying, accompanied with the use of cycles that include heating of the material to a temperature of 115° C. or less, high-speed impulse action of vacuum with a pressure change in the range up to 5 mm Hg for a time of less than 10 seconds, followed by exposure under vacuum and vacuum relief. 
     Both solution of nitric or sulphuric acids, their mixture and alkaline solution can be used as hydrolysis solution. 
     Technical result of the claimed method consists in. reducing the duration of the cellulose hydrolysis process, reducing the temperature of the processes while obtaining the required chemical and structural homogeneity of the cellulose.

The invention relates to the chemical industry, namely to the productionof the cellulose from all types of plant cellulose-containing material,chemically and structurally homogeneous, bleached and unbleachedcellulose, for paper, textile, medical, nitrocellulose industry(hereafter referred to as NC), paint and powder technologies, which canbe used for further processing in various industries: NC for powders,varnishes, enamels, textile, paper, medical, pharmaceutical, food etc.The wood of coniferous and hardwoods, cotton, flax, hemp, fruit shellsof cereal crops (oats, etc.), straw of cereals, as well as bamboo,miscanthus, amaranth, bagas, esparto, etc., are used ascellulose-containing raw materials.

There are many methods to obtain celluloses from wood and annual plants,and their number continues to grow. All methods for production ofcellulose are based on the fact that lignin, hemicelluloses and otherimpurities are taken to the destructive effects of chemical reagents andtechnological parameters much easier than the cellulose is.

The most common way of obtaining various celluloses is now the sulphatemethod. In the global pulp and paper industry, this method produces upto 90-95% of all types of celluloses. The sulphate process for thecellulose production belongs to the group of alkaline processes. In thesulphate process, the process is carried out batchwise at 160-180° C.,pH=13, pressure 0.7-1.5 MPa for 4-6 hours, under continuous cooking at atemperature of 190-200° C., the process takes about 30 minutes. The useof high (up to 1.5 MPa) pressure for boiler-reactors of large (up to 400m³ and more) volume with application of high temperatures complicatesthe technological process and its implementation. Despite the use ofhigh temperatures, the process of lignin separating at 145° C. takes 12hours, at 160-180° C. takes 4-6 hours, and only at 200° C. takes 30minutes. The introduction of additional constituents into the reagentcauses the release of gases that aggravate the ecology of the air basin,complicates the regeneration of solutions and the washing of celluloseusing a large amount of water and complicating the organization of waterrecycling.

The group of acidic processes for cellulose production includessulphite, inorganic (HNO₃, HC1), organic (acetic, monochloroacetic,etc.) acids are used as reagents, as well as ethylene glycol, phenol,butyl alcohol and other alcohols., as well as calcium-base solution,containing Ca(HSO₃)₂ with an excess of SO₂, supporting pH of thesolution at a level of 1.2-1.5. SO₂, which has strong acidic properties,penetrates into wood chips faster than the solution, so the solution isheated more slowly, otherwise incomplete delignification of wood occurs.The temperature of the solution in the production of paper pulp lies inthe range of 125-135° C., and for pulp for chemical industry is 145° C.,the processing time is up to 12 hours. The use of this method leads todeterioration of the sorption properties of resulting cellulose, itsstructural and chemical heterogeneity, reduced degree of crystallinity,and reduced stability of properties during storage.

In both methods, the obtained celluloses, especially when being producedby the sulphate method, the cellulose is molecularly heterogeneous. Thefinal characteristics of celluloses have increased spreads in viscosity,content of α-cellulose, etc.

To obtain better quality celluloses, the combined methods are used withthe addition of soda, chlorine-alkali, etc., which significantlycomplicate production.

A method for producing fibrous cellulose from a cellulose-containing rawmaterial is known, with the use of an aqueous solution of nitric acid asa delignifying agent (RU patent No. 2353626, IPC C08B1/04; D01F2/00,dated Oct. 25, 2007). In addition to nitric acid, the treating solutioncontains surfactants, an ammonium inorganic salt, or potassium or sodiumnitrate. Oxidative treatment is carried out in an alkaline-peroxidesolution containing sodium carboxymethyl cellulose and nonionicwater-soluble cellulose ether.

Disadvantages of this method are the use of a large number of reagentsand a number of additives, including surfactants, which are difficult todispose, and also involves the introduction of carboxymethylcellulose,which complicates the process, leads to its appreciation, the methodrequires a large consumption of water for cellulose washing.

A method for producing a cellulose by cooking wood chips of hardwood ina sulphite cooking solution and subsequent washing is known (RU patentNo. 2010069, IPC D21C 3/06 of Aug. 7, 1992). A mixture of crudeturpentine sulphite with a Na₂O content of 1.45-1.65% and total SO₂4.2-4.8%, and an aqueous solution of sodium carbonate with aconcentration of 90-110 g/l under their volumetric ratio from 100:3 to100:5 as a cooking liquor is used, and the cooking is carried out in thecooking liquor under the content of bound SO₂ 1.75-2.25% and Na₂O1.65-2.18% and pH 2.5-4.0 The cooking is carried out at a concentrationof total SO₂ of 3.8-4.5%.

This method is used to produce cellulose from wood chips of hardwoods orfrom low-resin wood species: spruce, fir.

The disadvantage of the method is the use of a composition of reagentsthat deteriorate the ecological environment of air and water basins. Theresulting cellulose does not have sufficient chemical and structuralhomogeneity.

The production of cellulose pulp is considered to be a capital-intensiveindustry with the use of large-scale equipment and consumption of a hugeamount of water.

A method for producing cellulose from non-wood plant raw material with acontent of native cellulose of not more than 50% and an aqueous solutionof sodium hydroxide (RU patent No. 2448118, IPC C08B 11/12, 1/00, 1/02 ,dated Sep. 11, 2010) is known. The raw material is washed with hot waterat the temperature of 40-75° C. under atmospheric pressure for 0.5-4.0hours, delignification is carried out at the temperature of 90-95° C.with an aqueous solution of nitric acid with a concentration of 2-8% for4-20 hours. Further cellulose is subjected to additional treatment withsodium hydroxide solution of 1-4% at a temperature of 60-95° C. for 1-6hours, which increases the duration of the process. This stage reducesthe degree of polymerization and leads to a deterioration in cellulosequality, in particular, to a decrease in the strength index.

As a prototype, a method for processing cellulose-containing rawmaterials has been selected (RU patent No. 2456394 of the IPC D21C 1/02,3/02, 9/10, 9/16, 11/04, C07G 1/00, dated Aug. 12, 2010), where theprocessing of cellulose-containing raw materials is carried out by thefollowing stages of the technological process: prehydrolysis(impregnation), cooking (hydrolysis) of lignocellulose in 30%hydrotropic solution for 1-3 hours , filtration of the obtainedcellulose, washing it with 30% hydrotropic solution, subsequent washingwith water, bleaching the cellulose with hydrogen peroxide in solutionof sodium hydroxide to obtain a bleached cellulose, treatment it with anacid solution followed by treatment with a solvent, filtration anddrying. Miscanthus or fruit shells of cereal crops, or straw of cerealcrops are used as cellulose-containing raw material.

In this method, miscanthus or fruit casings of cereal crops, or straw ofcereal crops are used to produce cellulose, however, the resulting pulpdoes not have sufficient chemical and structural homogeneity.

The final characteristics of celluloses obtained by the methodsdiscussed above have increased spreads in viscosity, alpha-cellulosecontent and other parameters.

The object of the invention is to provide a method for producing thecellulose of improved quality, with chemical and structural homogeneityfrom various types of cellulose-containing raw materials whilesimplifying and making cheaper the manufacturing process.

The desired object is achieved by processing a cellulose-containing rawmaterial comprising impregnating and hydrolysis of the raw material in ahydrolysis solution, filtration the resulting cellulose, subsequentwashing with water, filtration and drying, in which, according to theinvention, the impregnation and hydrolysis of the raw material in thehydrolysis solution, filtration of the resulting cellulose, washing withwater, filtration and drying are carried out with simultaneous use ofcycles involving the heating of the material to a temperature of 115° C.or less, high-speed vacuum-impulse action with a pressure change in therange up to 5 mm Hg for a time of less than 10 seconds, followed byexposure under vacuum, for example, until a constant temperatureachievement and vacuum relief.

As a hydrolysis solution, a solution of nitric or sulphuric acids ormixtures of nitric and sulphuric acids with a solution concentration ofnot more than 15.0% can be used at a ratio of the cellulose-containingraw material to the hydrolysis solution (module) no more than 1:15.

As a hydrolysis solution, an alkaline solution with a solutionconcentration of less than 30 grams/liter can be used at a ratio of thecellulose-containing feed to the hydrolysis solution (module) of notmore than 1:15.

As a hydrolysis solution, a solution of waste acids produced by theproduction of cellulose nitrates can be used, which is less expensive,since to return NC to the production their regeneration is required.

Annual cellulose-containing plants, after impregnation to maintain theoptimal fiber length for textiles, medical cotton wool, etc., aresubjected to defibration, to be used in NC-production these plants aresubjected to disintegration.

To increase the homogeneity of the cellulose and intensify subsequentoperations, the hydrolysis of the raw material in the hydrolysissolution for NC-production and other materials is carried out withsimultaneous disintegration.

Impurities dissolved in spent hydrolysis solution are separated, suchimpurities as lignin, hemicellulose, pectins, pentosans, etc. areseparated from the cellulose fiber, followed by their precipitation andthe production of fertilizers based on them according to a simplerscheme than in the production of sulphate cellulose.

If necessary, after washing the cellulose, its bleaching is carried outusing cycles that include heating of the material to a temperature of115° C. or less, high-speed vacuum-impulse action with a pressure changein the range up to 5 mm Hg for a time of less than 30 seconds, followedby exposure under vacuum, for example, until a constant temperatureachievement and vacuum relief.

If necessary, in order to maintain the integrity of the fiber length tothe maximum, some kinds of celluloses after washing with water andfiltration are squeezed out on the mesh or fabric filters by watervacuum-impulse suction and with passing the air heating medium throughthe fiber pulp layer and the mesh until the required moisture isachieved, followed by loosening of the packed cellulose.

The technical result is achieved due to the fact that all the stages ofthe technological process are accompanied by cycles, including heatingthe material to a temperature of 115° C. or less, high-speedvacuum-impulse action with a pressure change in the range up to 5 mm Hgfor a time of less than 10 seconds, followed by exposure under vacuumand vacuum relief. High-speed impulse action of vacuum is carried outwith the aid of a receiver and pipelines equipped with high-speedvalves. This leads to an intensification of mass transfer with theacceleration of the process of hydrolysis of the material and otheradvantages.

Impregnation in a hydrolysis solution.

Impregnation of cellulose-containing raw materials with simultaneousaction of cycles involving high-speed impulse actions of vacuum iscarried out in the hydrolysis solution. The action of high-speed impulsevacuum during impregnation improves wettability, degasses the treatedmixture, facilitating the penetration of the hydrolysis solution intothe raw materials' fibers, reduces the impregnation time, acceleratesthe dissolution of lignin, and separating the cellulosic part of the rawmaterial from other impurities.

Hydrolysis.

The prepared and impregnated with the hydrolysis solution raw materialis subjected to hydrolysis. Under a high-speed impulse action of thevacuum during the process of hydrolysis, from the capillaries of theheated cellulosic material and under impulse vacuuming, the moisturevapors, air and dissolved gases in the moisture are removed, the breakof a part of the membrane walls takes place and when the vacuum isreleased, the impregnation by the hydrolytic solution of not only thecapillaries but also the structure of the cellulosic material occurs.Thus, by the destruction of cellulosic material with high-speed andpulsed exposure to vacuum ensures the rapid penetration of thehydrolysis solution into the pulp material volume with the dissolutionof lignin, hemicellulose and other impurities from the destructiblecellulose to form chemically and structurally homogeneous cellulose fromall known types of cellulose-containing materials with bast fibers.

Under the high-speed impulse action of vacuum, a high homogeneity of thehydrolysis of the material is achieved due to hydrolysis conductingunder the impulse action of vacuum simultaneously over the entire volumeof the reactor within strictly specified temperature and the duration ofthe process values. The need for some additional reagents is eliminated.At constant temperature values, the required parameters of givencellulose are achieved by the number of cycles of the high-speed impulseaction of vacuum on the material, and not by the use of an elevatedprocess temperature.

Hydrolysis of various cellulose-containing raw materials can be carriedout in an alkaline or acidic medium. Hydrolysis in an alkaline mediumproceeds slower than in an acidic medium, in which the wettability ofthe material and the solution diffusion into the material improve. Withthe high-speed impulse action of vacuum, the wettability of thematerials is improved, so the hydrolysis of cellulose-containingmaterials can be carried out both in alkaline and in acid media. Takinginto account the universality of the technological process beingdeveloped, the preference is given to hydrolysis with acidic solutions,both from the viewpoint of simplifying the composition of the hydrolysissolution, and from the viewpoint of intensifying the hydrolysis process,lowering the process temperature, and obtaining high-qualitylow-viscosity cellulose. See examples 1 and 2 below.

By lowering the hydrolysis temperature and when the processing of thematerial is uniform, a greater maintenance of the crystalline part ofthe cellulose is achieved with an increase in its yield.

The alternation of the heating cycles for the material to the optimumtemperature, vacuum build-up and relief intensifies the mass transferwith the acceleration of the process of hydrolysis of the material andthe dissolution of lignin and other impurities, the destruction of thecellulose to the required viscosity for a given pulp, for example fortextiles, medical cotton, paper and nitrocellulose production. At thesame time, there is no need to use elevated temperatures and increasethe duration of the process, and, as the experimental work shows, thehydrolysis for different materials should be carried out at atemperature of 115° C. or less for approximately 10-60 minutes and,importantly, without the use of state technical supervision equipment.

At these temperatures, the required degree of polymerization isachieved, since under high-speed impulse action of vacuum theimpregnation is performed throughout the volume of the disintegratedmaterial at low reagent concentrations of 0.5-3.0% for 0.5-1.5 hours(example 3, which is given below).

Impregnation and hydrolysis of cellulose-containing raw materials iscarried out in a hydrolysis solution medium, where as a hydrolysissolution, a solution of nitric or sulphuric acids or mixtures of nitricand sulphuric acids with a solution concentration of not more than 15.0%is used at a ratio of the cellulose-containing raw material to thehydrolysis solution not more than 1:15.

The combined effect of acids favorably affects hydrolysis, improving thehomogeneity of cellulose from wood and annual plants.

Lignin is subsequently converted to organic fertilizer, which increasescrop yields.

Impregnation and hydrolysis of the cellulose-containing raw material isalso carried out in a medium, where an alkaline solution with aconcentration of less than 30 grams/liter is used as the hydrolysissolution at a ratio of the cellulose-containing raw material to thehydrolysis solution of not more than 1:15.

Impregnation and hydrolysis of cellulose-containing raw materials can becarried out with a solution of waste acids from the production ofcellulose nitrates, which is a mixture of nitric, sulphuric acids andwater. In spent acid, depending on the composition of the initialworking acid mixture, the nitric acid content reaches 20-28%, sulphuricacid up to 60% and water up to 20%, which allows creating the necessaryhydrolysis solution. The use of spent acids minimizes the cost of thehydrolysis solution.

To obtain the required values for the viscosity of celluloses fromannual plants for textiles, medical cotton wool, and some types ofpaper, etc., after impregnation, to keep the optimum length, the fibersare subjected to defibration. The process of hydrolysis of raw materialsin the hydrolysis solution is activated when being combined withdisintegration of, for example, wood up to 10-50 microns, whichincreases the homogeneity of the cellulose and intensifies subsequentoperations.

Obtained cellulose filtration.

After the hydrolysis of the cellulose-containing raw material in thehydrolysis solution medium is completed, the obtained cellulose isfiltered to separate it from the spent hydrolysis solution while usingthe above cycles, including the high-speed impulse action of vacuum. Agreat pressure drop on the filtering material increases the productivityof the process of separating the hydrolysis solution with the impuritiesdissolved therein from the cellulose fiber. Dissolved in the spenthydrolyzed solution impurities are subsequently precipitated togetherwith lignin.

Washing with water.

After filtration of the obtained cellulose, a washing is carried outwith the simultaneous use of the above cycles, including a high-speedimpulse action of vacuum, with water heated to 50-70° C., further at atemperature of 15-25° C. to remove the residues of the hydrolysissolution adsorbed on the surface of the lignin fiber and othersimpurities and low molecular weight hydrolysis products. At the sametime, mass-exchange processes are intensified, especially when boilingwater during impulse vacuuming throughout the volume of the solution.The cellulose is washed until neutral pH.

After washing, if necessary (for medical cotton, textile, paper,nitrocellulose varnishes and enamels), the cellulose is bleached.Bleaching is performed mainly by hydrogen peroxide with using cyclesthat include heating of the material to a temperature of 115° C. orless, high-speed vacuum-impulse action of vacuum with a pressure changein the range up to 5 mm Hg for a time of less than 10 seconds, followedby exposure under vacuum and vacuum relief.

Filtration.

Upon completing cellulose washing with water, it is filtered usinghigh-speed impulse actions of vacuum, similar to filtration afterhydrolysis. The separated washings are sent for regeneration to bereused.

Drying.

Drying of cellulose is carried out using the above cycles, includinghigh-speed impulse action of vacuum, which makes it possible to obtaincellulose less than 10% moisture, due to better desorption of surfacemoisture and positively directed pressure gradients of temperature andmoisture of cellulose. At a cellulose temperature of less than 100° C. adeeper and uniform drying takes place.

If necessary, for fibrous materials (textile, etc.) and before drying,the cellulose washed and filtered from the washings is squeezed on themesh or fabric filters by high-speed impulse vacuum suction of waterwith the passing of an air heating medium through a layer of fibrouscellulose and a mesh up to not more than 10% of moisture. Subsequently,the compacted cellulose is loosened.

Therefore, the use of high-speed impulse of vacuum actions at all stagesof the process of obtaining cellulose gives the following advantages forthe process: reducing the duration of cellulose hydrolysis process by anorder of magnitude, the possibility of creating closed-loop watercirculation, as well as hydrolysis and bleaching solutions, decrease ofprocess temperatures when obtaining the desired chemical and structuralhomogeneity of material, with achievement a greater maintenance of thecrystalline part of cellulose with a faster degradation of the amorphouspart of cellulose, and the possibility of obtaining the desired grade ofcellulose from any cellulose-containing material. The exclusion ofadditional chemicals from the hydrolysis solution improves theenvironment not only of the air basin, but also of the water basin byreducing the volumes of washing water with the organization of theirregeneration process. The regeneration of used hydrolysis, bleachingsolutions and washing water is greatly simplified. The technology ofseparating lignin and other impurities from cellulose and thetechnological process for obtaining high-quality homogeneous celluloseare simplified.

EMBODIMENT Example 1

Experimental work for the production of homogenized cellulose hascommenced with the production in the laboratory scale of hydrolyzedcotton cellulose from cotton linter not by alkaline cooking in a mediumof 10-15 grams/liter of alkali, but in an acidic medium.

In this case, all processes are carried out with the simultaneous use ofthe above cycles, including high-speed impulse actions of vacuum.

Under high-speed impulse of vacuum actions, the cotton lint isimpregnated with a 2.0% solution of spent acid from the production of NCfor 15 minutes at a temperature of 95° C.

Hydrolysis of linters is combined with disintegration up to 50-100microns in a laboratory apparatus. In the receiving tank underhigh-speed impulse actions of vacuum in the medium of a given hydrolysissolution, the viscosity of cellulose decreases to 5-10 cPs. Further, thecellulose is filtered, washed, and squeezed out on a centrifuge.Cellulose for nitrocellulose varnishes and enamels is bleached underhigh-speed impulse actions of vacuum with a mixture of aqueous solutionsof alkali concentration of 5 grams/liter and hydrogen peroxide ofconcentration of 8 grams/liter at 75° C. for 30 minutes. Bleachedcellulose is separated from the solution, washed, squeezed and dried byhigh-speed impulse actions of vacuum.

Technical parameters of the obtained cellulose: weight part ofalpha-cellulose amounts to 97-98%, wettability—167.5 g, dynamicviscosity—8.3 mPa.s, humidity—8%. Therefore, the production of cottoncellulose was proved to be not by alkaline, but acid hydrolysis. Thecellulose produced has a lower viscosity, high bleach and solubility ofthe samples of varnishes and enamels in a combined solvent, reaching98.5%, the varnishes are transparent.

Example 2

Obtaining of medical cotton from long-fiber cotton in the laboratoryconditions. At alkaline cooking, NaOH solution of 25 g/liter is used inthe process; the process is carried out at a module 1:20, at atemperature of 140° C. for 4 hours.

In the laboratory, the hydrolysis of cotton is carried out using allcycles, including high-speed impulse action of vacuum, by 2.5% melangesolution at 60° C. and module 1:7.5 module for 50 minutes. Impregnationof cotton is carried out with a change in pressure by high-speed impulseactions of vacuum up to 10 mm Hg. After hydrolysis, the hydrolysissolution is filtered from cotton. The hydrolysis solution is regeneratedand recycled again. The fiber is washed with water at a temperature of60° C. and further water at a temperature of 20° C. with a modulus of1:7.5 to neutral medium. Washing water after a two-stage (10 and 5 μm)filtration and adjustment for pH is re-used. The washed fiber isbleached with a mixture of aqueous alkali solutions with a concentrationof 3 grams/liter and hydrogen peroxide of 8 g/liter at 70° C. for 30minutes at high-speed pulsed actions of vacuum. Then, the bleachingsolution is separated from the cellulose; the solution is filteredtwice, regenerated and recycled. Then the washing of cellulose withwater at a high-speed impulse action of vacuum follows. Water athigh-speed impulse actions of vacuum is also filtered, adjusted for pHand reused. Bleached, washed cellulose is squeezed out on a continuous,conveyor mesh or fabric filter with pressure rollers and then dried bypassing an air-heating medium with a temperature of 100-115° C. througha cellulose layer and a mesh to 5-10% humidity by high-speed impulseactions of vacuum followed by loosening of the packed cellulose.

The obtained medical cotton wool is soft, satisfies the requirements ofTU in terms of parameters, and has an increased wettability. Humidity is8%; degree of bleaching is 80%.

Example 3

Experimental work on obtaining textile fibers from flax and hemp.

Stems of hemp, like flax, after drying are subjected to preliminaryhydrolysis at a temperature of 95° C. by a melange solution with aconcentration of 3.0% with a modulus of 1:7.5 when using the cyclesinvolving high-speed impulse action of vacuum. The impregnated fiber issubjected to hydrolysis, where it is brought to the required viscositystandards.

In order to obtain long fibers for textiles, medical cotton, linen andhemp paper, they are washed twice with water at a temperature of 60° C.and further at a temperature of 20° C. to neutral medium, while usingcycles with high-speed pulsed action of vacuum, dried at a temperatureof 95° C., and flax and hemp stems are passed through grooved rollerswith a clearance of 1.0-1.5 mm, with the crushing of the stems, and thepartial separation of fibers from the shover is scutching machines.After filtration the washed fiber is bleached with an alkaline-peroxidesolution, the solution is separated, and the fiber is washed andsubjected to squeezing out and drying on a continuous, conveyor-typemesh device with pressure rollers by passing an air heating medium witha temperature of 98° C. and by high-speed impulse actions of vacuumthrough a fiber layer and a mesh. Drying fiber is proceeded up to 10%moisture, the loosened on a roller machine and then packed into bales.The degree of polymerization of linen fibers is—10,000, the degree ofpolymerization of hemp is 8,000.

Example 4

Production of cellulose from hemp for production of NC with thesimultaneous use of cycles involving high-speed impulse actions ofvacuum through all stages of the process.

Under laboratory conditions, after impregnating the fiber in a 3%melange solution, the fiber is disintegrated during hydrolysis in asolution medium at a temperature of 95-98° C. at a modulus from 1:5 to50-100 μm, the cellulose viscosity is reduced to 5-10 caps. Thehydrolysis solution is also separated from the fiber. The hydrolysissolution is filtered out, lignin and impurities are precipitate, andafter regeneration, the solution is recycled. Cellulose, designed tomanufacture NC for nitro-varnishes and enamels, is bleached in anaqueous alkaline-peroxide solution. The solution is filtered,regenerated and recycled. The bleached cellulose is washed, squeezes outand dried. Cellulose fibers are washed to a neutral medium, squeezed outin a centrifuge or screw-press at high-speed impulse actions of vacuum.In the press, cellulose is pressed through a heated conical press devicewith matrices and is squeezed out to a humidity of 15-20%. By vacuumtransport the cellulose as a dense layer enters a vacuum-impulsecontinuous dryer and is dried at a temperature of 110° C. for 30 minutesto moisture content of not more than 10% and then is packaged. At theconsumer's plant, the cellulose is impregnated by high-speed impulseactions of vacuum in one or another solution and spreads onto fibers.

Example 5

Experimental work on obtaining sulphate hydrolysis wood cellulose wascarried out using cycles involving high-speed impulse actions of vacuumat all stages.

Wood chips of a thickness 5 mm, width of 10 mm, and a length of 14 mmare impregnated under high-speed impulse actions of vacuum with asolution of sodium hydroxide and sodium sulphide at a concentration of10 g/l at 95° C., module 1:7.5 with a pressure change of up to 10 mm Hgfor 30 minutes. Further, the chips are disintegrated in an alkalinehydrolysis solution in a laboratory disintegrator to a particle size of50-100 μm. Under high-speed impulse actions of vacuum at 95° C., thehydrolysis of disintegrated chips in an alkaline medium is brought up to10-15 cps for 1 hour. The hydrolysis solution with dissolved lignin andother impurities is filtered through woven metal meshes with mesh sizeof 50, 10, and 5 μm. After separation of hydrolysis solution, thecellulose fiber is washed with water at a temperature of 60° C. andwater at a temperature of 20° C. to obtain neutral medium. For betterpurification from impurities and finely dispersed destructed amorphouscellulose the washed cellulose is subjected to additional acidhydrolysis with a 3.0% melange solution at 90-95° C. using high-speedimpulse actions of vacuum for 60 minutes to reduce the celluloseviscosity of 9-10 cPs. The hydrolysis solution is filtered. The fiber iswashed, squeezed out in a laboratory centrifuge and dried to 8-10%moisture. For the production of cellulose for varnishes and enamels, itis bleached with a mixture of a solution of alkali (Noah) concentrationof 4-5 g/liter and hydrogen peroxide of 10 g/liter at 70-75° C. for 15minutes, followed by filtration of the bleaching solution, washing,squeezing and drying at 115° C. to a moisture content of 10% incellulose.

Alpha-cellulose content amounts to 96-97%, wet ability is 150-160 g,humidity is 8-10%, viscosity is 6-9 caps, and degree of polymerizationis 260.

Example 6

In laboratory conditions, the wood chips are impregnated with a solutionof melange with a concentration of 2.5% at 95-98° C. and a module of1:7.5 with the simultaneous use at this and subsequent stages of cyclesinvolving high-speed impulse actions of vacuum with a pressure change upto 10 mm Hg for 30 minutes. The chips are disintegrated in a hydrolysissolution up to a particle size of 50-100 μm. Required viscosity ofcelluloses is achieved during the disintegration process.

For wood with high resin content, the required viscosity values areachieved by high-speed impulse actions of vacuum. The hydrolysissolution is filtered by a high-speed impulse actions of vacuum through astainless mesh with cells of 10 and 5 μm, regenerated as per chemicalcomposition with the organization of the solution circulation in aclosed cycle way. The separated cellulose is washed twice with water ata temperature of 50-60° C. and then with water at a temperature of 20°C. Washing water is filtered by high-speed impulse actions of vacuumthrough a stainless mesh with cell sizes of 10 and then 5 μm. Water isregenerated according to Ph with the organization of closed watercirculation cycle. Washed cellulose is bleached with a mixture ofaqueous solutions of NaOH with a concentration of 3-6 grams/liter andhydrogen peroxide with a concentration of at least 8 grams/liter at atemperature of 50-75° C. for 30 minutes, followed by stepwise filtrationand regeneration of the solution of washing water and organization ofthe solution and water recycling. Bleaching of cellulose is requiredonly for the production of transparent nitrocellulose varnishes andenamels. The resulting cellulose is squeezed out in a centrifuge withthe use of suction of water with high-speed impulse actions of vacuum.In a screw-press, the cellulose is pressed to a humidity of 15-20%through a heated conical press device with a cowl and then through thematrices. Drying of cellulose is carried out in a vacuum drier ofcontinuous operation with the use of high-speed impulse actions ofvacuum at a temperature of 110° C. to a humidity of 10%.

The content in the cellulose produced of alpha cellulose is 96-97%,wettability is 150-160, viscosity is 5-9 cPs, humidity is 4-8%, anddegree of polymerization is 220-240.

Example 7

In the laboratory conditions, the verification of the possibility toproduce sulphite wood cellulose using cycles involving high-speedimpulse actions of vacuum at all stages and disintegration of the chipsin sulphuric acid medium has been tested. For the production of sulphitecellulose the impregnation of wood chips is carried out by sulphurousacid (H₂SO₃), as well as the disintegration of chips in the medium ofthis hydrolysis solution up to 50-100 μm is provided with a solution ofthis acid at a concentration of 10% at a temperature of 85-75° C. for 1hour. Further, the hydrolysis solution containing the lignin solutionand other impurities is filtered off. The fiber is washed to neutralmedium, and squeezed out in a centrifuge. Further, the wood chips areimpregnated with 8.0% nitric acid, without the use of a solution ofCa(HSO₃)₂, without SO₂, penetrating into the wood chips faster than thesolution, and without the use of alcohols (butyl and others), andwithout the use of phenol, ethylene glycol and organic acids (acetic,monochloroacetic and other acids).

The hydrolysis solution is separated in a centrifuge with theprecipitation of dissolved impurities. The fiber is washed to a neutralmedium, squeezed out in a centrifuge and dried to 10% moisture content.

If necessary, cellulose is bleached with NaOH solution in a mixture withhydrogen peroxide with separation, solution regeneration, washing anddrying of cellulose up to 10% moisture content.

Alpha-cellulose content reaches 97%, wettability is up to 150 g, degreeof polymerization is 240, and humidity is 10%.

Consequently, under high-speed impulse actions of vacuum during thehydrolysis of wood chips, and when the process is combined withgrinding, we obtain the sulphite cellulose from wood chips in a two-stepregime: first in an alkaline solution of sodium hydroxide and sodiumsulphide, then after separation of the alkaline solution and washing ina melange solution to regulate the regimes to obtain finished productswith improved characteristics of cellulose.

What is claimed is:
 1. A cellulose production method by processing acellulose-containing raw material comprising impregnating and hydrolysisof the raw material in a hydrolysis solution, filtration the resultingcellulose, subsequent washing with water, filtration and drying,wherein, the impregnation and hydrolysis of the raw material in thehydrolysis solution, filtration of the resulting cellulose, washing withwater, filtration and drying are carried out with the use of cyclesinvolving the heating of the material to a temperature of 115° C. orless, high-speed vacuum-impulse action with a pressure change in therange up to 5 mm Hg for a time of less than 10 seconds, followed byexposure under vacuum and vacuum relief.
 2. The method as claimed inclaim 1, wherein as a hydrolysis solution, a solution of nitric orsulphuric acids or mixtures of nitric and sulphuric acids with asolution concentration of not more than 15.0% is used at a ratio of thecellulose-containing raw material to the hydrolysis solution not morethan 1:15 is used.
 3. The method as claimed in claim 1, wherein analkaline solution with a concentration of less than 30 grams/liter isused as the hydrolysis solution at a ratio of the cellulose-containingraw material to the hydrolysis solution of not more than 1:15.
 4. Themethod as claimed in claim 1, wherein a solution of spent acids fromnitrocellulose production is used.
 5. The method as claimed in claim 1,wherein a one-year cellulose-containing plant raw material is subjectedto defibration after being impregnated in a hydrolysis solution.
 6. Themethod as claimed in claim 1, wherein the hydrolysis of the raw materialin the hydrolysis solution is carried out simultaneously with rawmaterial disintegration to increase the homogeneity of the cellulose andintensify subsequent operations.
 7. The method as claimed in claim 1,wherein the dissolved in a spent hydrolysis solution impurities areseparated.
 8. The method as claimed in claim 1, wherein after cellulosewashing and filtration the washing water is regenerated to organizewater rotation.
 9. The method as claimed in claim 1, wherein afterwashing the cellulose, its bleaching is carried out using cycles thatinclude heating of the material to a temperature of 115° C. or less,high-speed impulse action of vacuum with a pressure change in the rangeup to 5 mm Hg for a time of less than 30 seconds, followed by exposureunder vacuum and vacuum relief.
 10. The method as claimed in claim 1,wherein after cellulose washing with water and filtration to maintainthe integrity of the fiber length to the maximum, the cellulose issqueezed out on the mesh or fabric filters with pressure-exertingrollers by water vacuum-impulse suction and with passing the air heatingmedium through the cellulose fiber layer and the mesh until the requiredmoisture is achieved, followed by loosening of the packed cellulose.